what is the meaning of "Weak dominance in heterozygote"?

Answer 1

This means that the zygote recieved both a dominant and reccessive gene from it's parents, as opposed to "strong dominance", where a zygote recieves two dominant genes.

Answer 2

A heterozygote means two different alleles of the same gene. Since the two alleles are different, it is likely that one is more active or more efficient than the other. If this difference is small/minor, then the 'stronger allele' would exhibit 'weak dominance' over the weaker allele.

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